Replacing Vista with Windows 7

I've imported a Vista machine to my Mac. For a number of issues, I want to replace the Vista machine by a Windows 7 one. Can I simply migrate a second computer to my Mac? Will the second computer remove and replace to Vista one?

 

Let me be a bit more specific. I basically want to replace the Virtual Machine on my Mac with another Virtual Machine. I assume that if I try simply importing a second VM that I'll end up with two VMs. Or is my assumption wrong? Will Parallels automatically remove the exiting VM when I try to import a second one? Or, do I need to remove the first VM before importing the second one? If so, how do i go about doing that?